On Wed, 29 Nov 2006 04:43:14 GMT, Owen Duffy wrote:


John,

Your terminology has me confused.

When you say you expect to see resonance between 6-8MHz, I understand
resonance to mean zero reactance at that frequency. Then you tell us
you expect to see lots of reactance. They are inconsistent.

Then you tell me that you expect to see a dip in SWR at the 1/4 wave
length. I am guessing, but I think you probably mean the frequency
where the vertical is a quarter wavelength long electrically.

If you drive the vertical at the base in series, you would expect to
observe resonance (ie no reactance) somewhere around the quarter wave
frequency.

If you shunt feed it further up, the shunt feeding arrangement acts as
an impedance transformer, and it is unlikely that you will see zero
reactance (ie resonance) at the same frequency as if you series fed
the vertical at the base. A feature of shunt feeding typically is that
it is reactive, and you have to tune out the reactance, adjusting the
tap point up or down to get the desired feed impedance.

Owen
Sorry for the confusing terminology but I am confused!
The testing I have done so far with this 28 foot antenna has been
series fed. The results obtained have been consistant with the Eznec
models.

I believe my current direction requires I puzzle out the Gamma match
in Eznec.
John Ferrell W8CCW